1. Field of the Invention
The invention relates to a closed audio circuit for clarity enhancement and eavesdropping prevention, and to a method for its implementation the same.
2. Background of the Invention
Closed audio circuits have been used for a variety of audio communication applications, for purpose of audio signal enhancement, noise cancellation, etc. For example, noise control is an active or passive means of reducing sound emissions, often for personal comfort, environmental considerations or legal compliance. Active noise control is sound reduction using a power source. Passive noise control is sound reduction by noise-isolating materials such as insulation, sound-absorbing tiles, or a muffler rather than a power source.
Modern active noise control generally is achieved through the use of analog circuits or digital signal processing. Adaptive algorithms may be applied to analyze the waveform of background aural or nonaural noise, then based on a specific algorithm generate a signal that will either phase shift or invert the polarity of the original signal. This inverted signal (in antiphase) is then amplified and a transducer creates a sound wave directly proportional to the amplitude of the original waveform, creating destructive interference. This effectively reduces the volume of the perceivable noise.
Various efforts have been disclosed for eavesdropping prevention and/or audio clarity enhancement. For example, U.S. Pat. No. 5,796,789 discloses a telephone alerting device for connection to a telephone line and a telephone. When the telephone is off-hook, the device will generate a visual and an audio alarm if an additional telephone connected to the same line also goes off-hook. U.S. Pat. No. 8,369,534 discloses a switching noise cancellation method for microphone-speaker combinations used in two way audio communications. U.S. Pat. No. 6,064,743 discloses a wavetable audio synthesizer with waveform volume control for eliminating zipper noise. U.S. Pat. No. 8,670,554 discloses a method and apparatus for encoding multiple microphone signals into a source-separable audio signal for network transmission. U.S. Patent Application Publication No. 2015/0080052 discloses a method for eavesdropping prevention pairing a peripheral unit to a telephone via an interface unit.
However, none of the above prior art deals with situations when individuals in a group audio communication need to have private conversations without risking the eavesdropping of others as well as require enhanced clarity to prevent misunderstanding, no matter whether the conversations are conducted indoors or outdoors.
It would be desirable to have a closed audio circuit to prevent eavesdropping in combination with the capabilities of real-time sound source isolation for optimized audio clarity during a multiple-user audio communication session.